The Enterprise is leading thirty-thousand colonists on a six month trip to establish a strategically important colony. Just after they make their first attempts at settling in, Spock discovers a nearby moon has two important features. It is made of a very valuable ore and is also unstable. If it blows, all the colonists will be killed.
In Voyages of Imagination, Dean Wesley Smith reflects: "Kris and I wrote book five in that series as well, but Diane was supposed to write one, two, and six. The first book turned out to be harder than she expected, so John and her called me in to write book two from her outline, and then we worked on it together some, I think. Memory fades."